FSc ICS Notes Physics XII Short Questions & Definitions Chapter 21 Nuclear Physics

FSc ICS Notes Physics XII Short Questions & Definitions Chapter 21 Nuclear Physics 2nd Year Physics Notes Online Taleem Ilmi Hub

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Nuclear Physics: The branch of Physics that is concerned with nuclear structure, properties, and reactions, and their applications, e.g., in producing nuclear power or using radioisotopes.

Atom models: Several theories have been successively proposed, called atom models. Thus we have the Thomson atom model, Rutherford nuclear atom model,

Bohr atom model, Sommerfeld’s atom model, and Vector atom model.

Thomson atom model: According to this model, atom has a uniform density, there is no empty space inside the atom and the electrons are in stable equilibrium with the positive charges.

Rutherford nuclear atom model: He proposed that the mass and positive charge of the atom were not distributed uniformly over the volume of the atom, but instead were concentrated in an extremely small region at center of atom.

Bohr atom model: According to it, the electron revolves in a circular orbit around the nucleus, when moving in the allowed orbits does not radiate energy. Emission or absorption occurs when an electron makes transition from one orbit to another.

Sommerfeld’s atom model: He gave the idea that electrons move in elliptical path and nucleus must lie at one of the focus. And two coordinates which varies periodically, namely the radius vector and the angle that the radius vector makes with the X-axis.

Vector atom model: The vector representation of the orbital model is called vector model.

Atom: The smallest particle of an element that can exist either alone or in combination with others of the same or of another element.

Nucleus (or Atomic nucleus): The positively charged dense central part of an atom.

Atomic number (or Charge number, or Proton number): The number of protons in the nucleus of an atom.

Mass number (or Nucleon number):

• The sum of the number of protons and neutrons in the nucleus of an atom.
• Nearest integer to its mass when measured in atomic mass units.

Nucleon: A particle found in the nucleus of atoms, i.e., a proton or a neutron.

Electron: Elementary particle of negative charge(-1.602 C) and rest mass 9.1096x10(-31) kg.

Proton: An elementary particle of positive charge (+1.602 C) and rest mass 1.673 x 10(-27) kg.

Neutron: An elementary neutral particle having a rest mass of 1.6749 x 10(-27) kg.

Neutron number: The number of neutrons in the nucleus of an atom.

Periodic table: A table of elements arranged in order of increasing proton number to show the similarities of chemical elements with related electronic configurations.

Isotopes: Atoms of same atomic number but different mass number.

Ion: A charged particle consisting of an atom, or group of atoms, that has either lost or gained electrons.

Deuterium: Element whose atoms consist of deuterons.

Deuteron: Atomic nucleus consisting of one proton and one neutron.

Tritium: Triple heavy hydrogen composed of atoms having tritons as nuclei.

Triton: Radioactive hydrogen nucleus composed of one proton and two neutrons.

Neutrino: One of the fundamental particles of matter of zero mass and zero charge.

Meson: One of the fundamental particles of matter found with a positive, negative, or zero charge and with a mass from 210 to 1000 times that of the electron.

Xenon (54Xe): A colourless odourless gas belonging to group 0 of the periodic table. It is present in the atmosphere from which it is extracted by distillation of liquid air. The element is used in fluorescent lamps and bubble chambers.

Caesium (55Cs ): A soft silvery white metallic element. Cs133 is the natural isotope. Cs137 is used as a γ - source. It has the lowest ionization potential of all elements, hence it is used in photoelectric cells.

Mass spectrograph: An apparatus for the determination of the exact masses of atomic particles, by photographing the mass spectrum produced, which obtains through suitably disposed magnetic and electric fields.

Mass spectrum: A spectrum obtained with a mass spectrometer or spectrograph in which a beam of ions is arranged in order of increasing charge to mass ratio.

Mass spectrometer: An apparatus for obtaining the mass spectrum of a beam of ions by means of suitably disposed magnetic and electric fields.

Mass defect (or Mass deficit): The arithmetic difference between the mass of a nucleus and the larger combined mass of its constituent particles.

Binding energy (of a nucleus):

• The energy needed to break up a nucleus into its constituent particles.
• The energy equivalent to the difference between the mass of the nucleus and the sum of the masses of its constituent nucleons.

Radioactive: Describing an element or nuclide that exhibits natural radioactivity.

Radioactivity: The spontaneous, uncontrollable decay of an atomic nucleus with the emission of particles and gamma rays.

α-particles: A helium nucleus emitted from the nucleus of a radioactive atom.

β-particles: Electron emitted from the nucleus of a radioactive atom.

γ-rays: High energy electromagnetic wave emitted from the nucleus of a radioactive atom.

Nuclear reaction: A reaction within atomic nucleus resulting a change in the identity of the nuclei.

Nuclear transmutation: A change in the atomic number of an atom.

Nuclear change: A change in the identity of atomic nuclei.

Radioactive decay: The spontaneous disintegration of unstable (radioactive) nuclei to give other a lighter more stable nuclei, accompanied by the emission of particles and/or photons.

α-decay: A type of radioactive decay in which the unstable nucleus emits a helium nucleus.

β-decay: A type of radioactive decay in which a nucleus emits, for instance, an electron.

γ-decay: A type of radioactive decay in which γ-rays are emitted by the specimen.

Decay constant (λ): The ratio between the number of nuclei decaying per second and the total number of nuclei.

Activity (A): For a radioactive substance, the average number of atoms disintegrating per unit time. Mathematically ; A = ΔN / Δt

Curie: A unit of radioactivity, equivalent to the amount of a given radioactive substance that produces 3.7 x 10(10) disintegrations per second.

Parent element: A given nuclide that undergoes radioactive decay to another specified nuclide, called the daughter element.

Daughter element: A given nuclide produced by radioactive decay from another nuclide, the parent element.

Radioactive series: A series of radioactive nuclides, each being formed by the decay of the previous one.

Radioactive dating: Any method for measuring the age of materials that depends on radioactivity.

Carbon-dating (or Radio-Carbon dating): It is a method of determining the age of objects up to 35000 years old containing matter that was once living, such as wood. Based on C14 radioactive decay and measuring its half life. .

Protactinium (91Pa231 ): A radioactive metallic chemical element, which is a member of the actinide series and occurs as a decay product in uranium ores.

Statistics:

• The field of study that involves the collection and analysis of numerical facts or data of any kind.
• The statistical description appropriate to the behaviour and properties of an ensemble of many atoms, molecules, etc., esp. as regards the distribution of energy among them

Half life: Time required to decay an element into half of its original quantity.

Artificial radioactivity: When high energy particles are bombarded on the stable nuclides, the nuclides after becoming unstable disintegrates with the emission of radiation.

Iodine(53I ): A dark violet nonmetallic element. There is one stable isotope, I127 , and fourteen radioactive isotopes. It is insoluble in water but soluble in ethanol and other organic solvents. It is required as a trace element by living organisms. It is used in medicine as a mild antiseptic.

Range of the particle: Distance traveled by a particle in a medium before coming to rest, after emission from a unstable nuclide.

Solid: The state of matter that has definite volume and definite shape.

Liquid: The state of matter that has definite volume, but no definite shape.

Liquefaction: The production of a liquid from matter in another physical state.

Gas: The state of matter that has neither definite volume nor shape.

Ideal gas: A theoretical gas consisting of infinitely small molecules which exert no forces on each other.

Scattering: The ‘spreading out’ of a beam of radiation as it passes through matter, reducing the energy moving in the original direction.

Absorption: A process in which a gas is taken up by a liquid or solid, or in which a liquid is taken up by a solid.

Lambert’s law: The law concerns the rate of absorption of radiation as it travels deeper into a medium. It states that equal thickness of the medium absorb equal proportions of the incident radiation. In other words, the intensity I of the transmitted radiation falls off exponentially with distance x in the medium:
I = Io e-μ x

where Io is the intensity of the initially incident radiation, and μ is the linear absorption coefficient of the medium.

Linear absorption coefficient: The coefficient μ in the Lambert’s law. It depends upon the energy of the photon and the properties of the medium. It varies with wavelength.

Fluorescence:

• It is the property of absorbing radiant energy of high frequency and re-emitting energy of low frequency in the visible region of electromagnetic spectrum.
• A type of luminescence in which the emission of electromagnetic radiation ceases as soon as excitation ceases.

Detector: A device that responds to any physical effect, used to indicate the presence of a signal or to measure it.

Radiation detectors: The devices which detect atomic particles, such as, α-particle, β-particles, fast moving protons, γ- rays, etc.

Wilson-cloud chamber (or Cloud chamber): An apparatus used to detect the passage of charged atomic particles by the tracks visible as a row of droplets, form in a special chamber.

Geiger counter (or Geiger-Muller counter): Instrument used for the detection and measurement of radioactivity. It is gas-filled radiation detector operated at high voltage in which the gas amplification effect produces a large discharge pulse after each primary ionizing event.

Geiger-Muller tube: Discharge tube that is activated by the passage of ionizing particles or rays.

Solid state detector ( or Semi-conductor detector): It consists of a semiconducting crystal in which electrons are not free to move, even though a voltage is applied through the crystal provides mobile electrons which are collected by the wires that apply the external voltage. Then the electrical pulse is amplified.

Supersaturated vapour: A vapour, the pressure of which exceeds the saturation vapour pressure at that temperature. It is unstable and condensation occurs in the presence of suitable nuclei or surfaces.

Vapour: A gas at any temperature at which it may be liquefied by pressure alone; i.e. a gas below its critical temperature.

Vapour pressure: The pressure exerted at a particular temperature by a vapour.

Adiabatic expansion: Spreading out or expanding of the gas in which not heat flows into or out of the system.

Erratic: Irregular or uncertain in movement; having no fixed course or direction.

Mica: A mineral consisting of complex silicates, characterized by a perfect separating along a line of natural splitting enabling the crystals to be split into very thin plates.

Cascade: A falling stream of something. A waterfall.

Scaler: A device that produces an output pulse when a specified number of input pulses have been received. It is usually used for counting purposes.

Quenching: The process of preventing a continuous discharge in a Geiger counter so that the incidence of further ionizing radiation can cause a new discharge.

Quenching gas: A gas or vapour such as ether or a halogen gas is introduced into the tube of Geiger counter to prevent a continuous discharge.

Nuclear reaction: A reaction within atomic nucleus resulting a change in the identity of the

nuclei.

Reactants: In a nuclear reaction, fast moving particle and target nucleus are called reactants.

Products: In a nuclear reaction, the newly obtained particle and the recoil nucleus are called products.

Paraffin: A whitish translucent waxy combustible solid consisting of a mixture of hydrocarbons, obtained as residue from the distillation of petroleum and used esp. in candles, cosmetics, and polishes, and for coating and sealing.

Nuclear fission (or Fission reaction): The splitting of a heavy nucleus into nuclei of medium mass, with the release of nuclear energy.

Fission chain reaction: A continuing process of nuclear splitting

Critical mass: The minimum mass of a material that can sustain a nuclear chain reaction.

Critical volume: The volume occupied by the mass of a material that can sustain a nuclear chain reaction.

Atomic bomb (or Atom bomb): A bomb in which the explosion is caused by a fast uncontrolled fission reaction.

Cadmium ( 48Cd112 ) : A soft bluish metal, used in low melting point alloys to make solders in some batteries.

Nuclear reactor (or Atomic reactor):

• A device in which the controlled fission of radioactive material produces new radioactive substances and energy.
• A device in which nuclear reactions take place on a large scale.

Nuclear power station: A power station using a nuclear reactor as the source of energy.

Power station (or Generating station): A complete assemblage of plant, equipment, and the necessary buildings at a place where electric power is generated on a large scale.

Thermal power station: A power station using furnace as the source of energy.

Fission fragments: In a nuclear fission reaction, the product nuclei are called fission fragments.

Hydrocarbon: Chemical compounds that contain only carbon and hydrogen.

Moderator: A substance used in nuclear reactors to reduce the speed of fast neutrons produced by nuclear fission.

Heavy water ( D2 O): Deuterium oxide is called ‘heavy water’; it is used as a moderator and coolant in some types of nuclear reactors.

KANUP (Karachi Nuclear Power Plant): Here heavy water is used as a moderator, and transportation of heat, from reactor core to heat exchanger, also heavy water is used.

Nuclear waste: Used fuel in a nuclear reactor. Nuclear fuel once used for charging, keep on operation for few months, then fissile material begins to decrease. Then this used fuel is removed, which is still radioactive and injurious and harmful to the living things.

Dumping: To throw down nuclear waste in the bottom of old salt places, thousands of meters below the surface of the Earth.

Contaminate: Make impure by contact or mixture; pollute, corrupt, infect. Subject to contamination by radioactivity

Fast reactors: The types of fast reactors are research reactors, plutonium reactors, and breeder reactors.

Thermal reactors: The types of thermal reactors are boiling-water reactor, pressurized-water reactor, and liquid-metal reactor.

Research reactor: In this reactor uranium rods are placed inside a block of graphite. Fast moving neutrons are from fission of U235 are slowed down by graphite.

Plutonium reactor: It is used to produce plutonium that can be used in the atomic bomb as a fissionable material. The reactor contained a critical mass of U238 .

Breeder reactor: It is one in which a fissionable material is produced at a greater rate than the fuel is consumed.

Power reactor ( or Thermal reactor): A power reactor is a device to make use of the natural heat developed in a uranium reactor as source of huge power.

Boiling-water reactor: In it a stream of water circulates through the core. The heat turns the water to steam, which is then used to generate electricity.

Pressurized-water reactor (PWR): Here the heat is extracted in two-step process. Water circulates through the core under great pressure, to prevent its turning to steam. This hot water then in turn heats a second water system, which actually delivers steam to the turbine.

Liquid-metal reactor: The disadvantage of using water is that it has small heat capacity. A metallic medium would be much better for heat transfer. Liquid sodium could replace the pressurized water.

Reprocessing plant: There are two types of reprocessing plants; electromagnetic separator and gaseous diffusion plant.

Natural uranium: The element uranium naturally occurs in three isotopes which posses identical chemical properties. Wherever it is extracted it contains the three isotopes with 92U238 at 99.3 %, 92U235 at 0.7 % and 92U234 less than 0.001 %.

Enriched uranium: The uranium with greater percentage of U235 then natural uranium. It is done with the help of reprocessing plants.

Electromagnetic separator: It is identical in principle to the mass spectrometer. And depends for its action simply on the fact the U235 and U238 ions have different ratios of charge to mass. Here a sufficiently large current is needed.

Mass spectrometer: An instrument for producing ions in a gas and analyzing them according to their charge/mass ratio.

Gaseous diffusion plant: Gaseous diffusion separator depends on the slight difference in diffusion rate of gases of different molecular weight. U235 and U238 are pumped through a porous barrier and thousands of stages are required for fractional enrichment of the light isotope.

Core: The part of a nuclear reactor that contains the fissile material.

Fusion reaction (or Nuclear fusion): A reaction in which light nuclei combine to form a nucleus with medium mass, with the release of nuclear energy.

Mass defect (or Mass deficit): The arithmetic difference between the mass of a nucleus and the larger combined mass of its constituent particles.

Binding energy (of a nucleus):

• The energy needed to break up a nucleus into its constituent particles.
• The energy equivalent to the difference between the mass of the nucleus and the sum of the masses of its constituent nucleons.

Hurl: A rush or swirl of water; rushing water. A noisy rush or fall, esp. of stones etc. down a slope. The action or an act of hurling; a violent throw or cast.

Hydrogen bomb: It consists of a fission bomb surrounded by a layer of hydrogenous material, such as lithium deuteride.

Neutron bomb (or Cobalt bomb): It is made by covering hydrogen bomb with metallic cobalt. When it is exploded, neutrons emitted react with cobalt cover and form Co60 which three hundred times

powerful than radium.

Electromagnetic radiation: Transverse waves in space having an electric component and a magnetic component, each being perpendicular to each other and both perpendicular to the direction of propagation. These do not require any medium for its motion.

Cosmic radiation (or Cosmic rays): High energy particles, falling upon the Earth, apparently from beyond our solar system, consisting chiefly, if not entirely of charged particles.

Ozone (or Trioxygen) [O3 ]: A colourless gas, soluble in cold water and in alkalis. Liquid ozone is dark blue in colour and is diamagnetic (O2 is paramagnetic). It is produced in the stratosphere by the action of high-energy ultraviolet radiation on oxygen and its presence acts as a screen for ultraviolet radiation.

Ozone layer: The region of the upper atmosphere, at an altitude of 10 to 50 km (6 to 30 miles), containing significant amounts of ozone, which absorbs short ultraviolet light; esp. the region of maximum ozone concentration between 20 and 25 km (12 and 15 miles).

Vomiting: When sick, matter ejected from the stomach.

Troposphere: The lowest region of the atmosphere, extending to a height of between 8 and 18 km (5 and 11 miles) and marked by convection and a general decrease of temperature with height.

Stratosphere: The region of the atmosphere extending above the troposphere to a height of about 50 km (30 miles), in which in the lower part there is little temperature variation with height, and in the higher part the temperature increases with height. Formerly, the lower part of this region, up to a height of about 20 km.

Chlorofluorocarbons (CFC): Any of a group of exceptionally stable compounds containing carbon, fluorine, and chlorine (analogous to the hydrocarbons), which have been used esp. as refrigerants and

aerosol propellants.

Aerosol: An ultramicroscopic particles’ dispersion of a solid or liquid in a gas. The commonly used aerosol sprays contain an inert propellant liquefied under pressure.

Propellant: The inert compressed fluid in which the active contents in an aerosol container etc. are thrust out.

Toxic: Of the nature of a poison; poisonous.

Toxic smoke: The visible suspension of poisonous gases and other particles in air, due to given off by a burning or smoky vapour.

Biology: The science, which deals with the origin and life history of plants and animals including botany and zoology.

Biological: Pertaining to the science, which deals with the origin and life history of plants and animals including botany and zoology.

Becquerel (Bq): The Becquerel is the SI unit of radioactivity. 1 becquerel represents one disintegration, or other nuclear transformation, per second; 1Curie = 37x10(9) Bq

Curie: A unit of radioactivity, equivalent to the amount of a given radioactive substance that

produces 3.7 x 10(10) disintegrations per second.

Gray (Gy): The SI unit of absorbed energy dose per unit mass resulting from the passage of ionizing radiation through living tissue. One gray is an energy absorption of one joule per kilogram of mass.

Sievert (Sv): An SI unit of dose equivalent of ionizing radiation, defined as that which delivers one joule of energy per kilogram of recipient mass, and equal to 100 rem.

Rad: A unit of absorbed dose of ionizing radiation, defined as being equivalent to an absorption of 10(-2) joule of energy in one kilogram of material.

Rem (Roentgen equivalent man): This unit is the quantity of ionizing radiation such that the energy imparted to a biological system per gram of living matter by the ionizing particles present in the locus of interest has the same biological effectiveness as one rad of 200 to 250 kilovolt X-rays.

Relative biological effectiveness (RBE): A quality factor to get the equivalent dose (De ) of any absorbed radiation (D); De = D x RBE

Diarrhea (or Diarrhoea) : A condition of excessively frequent and loose bowel movements. Also, watery /semi-liquid discharge characteristic of this condition.

Radiation sickness: Less than a lethal dose (400-600 rem) the victim complains nearly after six hours of nausea, loss of appetite, vomiting and diarrhea. High doses ( > 2000 rem) result in brain damage, fits, coma and death within few days of exposure.

Cataract: A condition of partial or complete opacity of the lens of the eye.

Anaemia: A deficiency of red blood cells or their haemoglobin, often causing paleness.

Haemoglobin (or Hemoglobin): Hemoglobin is a protein that carried by red cells. It picks up oxygen in the lungs and delivers it to the peripheral

tissues to maintain the life of cells.

Leukaemia: Any of a group of very infectious and progressive diseases characterized by the gross overproduction of white blood cells , which accumulate and suppress other production of blood cells.

Chromosome: A threadlike structure of nucleic acids and protein that carries a set of linked genes and occurs singly in prokaryotes and in characteristic numbers, usually paired, in the cell nuclei of higher organisms.

Mutation: The action or process of changing; an alteration, a change.

Isotopes: Atoms of same atomic number but different mass number.

Radioisotope: A radioactive isotope of an element. Tritium, for example, is a radioisotope of hydrogen.

Biology: The science, which deals with the origin and life history of plants and animals including botany and zoology.

Fertilizer: Any material put in or on the ground, which contains plant food.

Mutation: The action or process of changing; an alteration, a change.

Chickpea: The seed of a dwarf pea, grown for food especially in Asia.

Pest: A fatal epidemic disease. A troublesome, or destructive insect which attacks crops, livestock.

Radioactive tracing: A method of tracing the course of an element through a biological, chemical, or mechanical system.

Radioactive tracers: Radio-isotopes used to trace the path or position of an element through a biological, chemical, or mechanical system.

Radioactive isotope: An isotope of an element that is radioactive.

Dosimeter: Any instrument or material used for measuring radiation dose.

Dosimetry: The measurement of radiation dose, the choice of method being determined by the quantity and quality of radiation delivered, the rate of delivery and the convenience.

Malignant: A disease liable to become progressively more severe; extremely virulent; very infectious. Now chiefly of a cancer or tumour: tending to spread to other parts of the body, or to recur after removal.

Tumor: An abnormal swelling or enlargement in any part of the body of an animal or plant; an excrescence. Usually a permanent swelling without inflammation, caused by excessive continued growth of cells in a tissue. .

Photosynthesis: The process in plants by which carbon dioxide is converted into organic compounds using the energy of light absorbed by chlorophyll, which in all plants except some bacteria involves the production of oxygen from water; any photochemical synthesis of a chemical compound.

Radioactive Tracers: A definite quantity of radioisotope introduced into a biological or mechanical system so that its path through the system and its concentration in particular areas can be determined by measuring the radioactivity with the detector.

Thyroid gland: The secreting organ in the upper part of the wind pipe of the voice organ in the body.

Hyperactive gland: The secreting organ with excessive function.

Liver: A large lobed glandular organ in the abdomen of vertebrate animals which secretes bile, detoxifies the blood, and is important in the metabolism and storage of major nutrients.

Radiotherapy: The use of beams of ionizing radiation, such as X-rays, energetic electrons, and the streams of gamma rays from the radioisotope cobalt-60, in the treatment of cancer.

Malignant tissue: A tissue liable to become progressively more severe; extremely virulent; very infectious. Now chiefly of a cancer or tumour: tending to spread to other parts of the body, or to recur after removal.

Encapsulate: Enclose in or as in a capsule.

Radiograph: The shadow photographs obtained in the process of radiography.

Radiography: The production of shadow photographs of the internal structure of bodies opaque to visible light by the radiation from X-rays, or by gamma-rays from radioactive substances.

Scanning: The process of exploring an area or volume in a methodical manner, in order to produce a variable electrical output whose instantaneous value depends on the information contained in the small area examined at each instant.

Kidney: Either of a pair of glandular organs of rounded shape with a shallow indentation on one side, situated in humans in the back of the abdominal cavity, which maintain the composition of the blood, removing waste nitrogenous and other matter and excreting it as urine.

Gravitational force: The mutual force of attraction between particles of matter.

Magnetic force: A force associated with the motion of electric charges.

Electric force: Force of attraction or repulsion between two un-like or like charged bodies.

Weak nuclear force: A short range nuclear force acting between nucleons and is responsible for the decay of nuclei.

Strong nuclear force: A short range attractive force acting between nucleons and holds nucleus together.

Microscopic: Very small; invisible without a microscope.

Microscopic level: The level or state of matter characterized by the actual properties of each individual elemental component. Quantum theory is typically an analysis of the microscopic state.

Macroscopic level: The level or state of matter characterized by the statistical properties of its components. Kinetic theory is an analysis of the macroscopic state.

Kinetic theory: A theory explaining physical properties in terms of the motion of particles.

Quantum theory: A mathematical physical theory originally introduced by Max Planck to explain the black body radiation from hot bodies, it deals with the mechanics of atomic and related systems in terms of quantities that can be measured.

Unification: A grand unification theory has been proposed which combine the strong and electroweak forces intro single framework.

Subatomic particles: A constituent part of an atom, i.e. electrons, protons and neutrons. Which are further made up of elementary particles.

Photon: A quantum of electromagnetic radiation that has zero rest mass, and energy equal to the product of the frequency of the radiation and Planck’s constant.

Leptons: A group of elementary particles including the electron, the muon, and the neutrino. They are distinguished from hadrons by their type of interaction.

Hadrons: A group of elementary particles, subdivided into the baryons and the mesons. The hadrons are distinguished from the leptons by their type of interaction.

Elementary particles (or Fundamental Particles, or Sub-atomic Particles): Invisible particles from which all matter is composed.

Quarks: A type of hypothetical fundamental particle postulated to make up other elementary particles.

Mesons: Elementary particles that are more massive than electrons but lighter than protons and neutrons. Mesons are thought to be involved in the exchange forces between nucleons in the nucleus.

Background radiation: The low intensity radiation resulting from the bombardment of the earth by cosmic rays and from the presence of naturally occurring radionuclides in rocks, soil, air, building materials, etc. When measurements of radiation are being carried out a correction must be made for the background radiation.

Cosmic rays: High energy particles, apparently from beyond our solar system.

Written By: Asad Hussain